Genuine GM Heating and Air Conditioning Defroster Valve 89018304 is a direct replacement part for select Cadillac, Chevrolet, GMC, and Hummer models manufactured between 2003 and 2014. This genuine OEM product is made by GM and has the manufacturer part number 89018304. It is designed to regulate the flow of air in the heating and air conditioning system and is sold without any warranty.